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Fungus spotlight: Ganoderma resinaceum (lacquered bracket)

I thought I’d share a little bit on the lacquered bracket, for those that may be interested. An interesting species of Ganoderma, particularly in the way in which is presents itself. Hopefully, for those interested in fungi, this post will be of use.

A tier of dried-out Ganoderma resinaceum brackets upon a hornbeam (Carpinus betulus). These were located around 2.5m up the main stem.

Colonisation strategy

Entering through exposed heartwood surfaces, Ganoderma resinaceum will typically begin its life as a parasite. However, upon death of the host, it may persist as a saprophyte (Deflorio et al., 2008b; Mattheck et al., 2015). Upon entering into heartwood, it may begin to also colonise sapwood (Watson & Green, 2011).

Rot

The type of rot induced by Ganoderma resinaceum is not fully understood, though it is considered to selectively delignify its host (Deflorio et al., 2008a; Mattheck et al., 2015; Rayner & Boddy, 1988; Schwarze & Ferner, 2003; Watson & Green, 2011). Lonsdale (1999) remarks that it may oft be confused with Ganoderma lucidum, making differentiation of rot characteristics between the species difficult, though it is considered that Ganoderma resinaceum induces a more ‘complete’ rot that other Ganoderma species.

Areas affected

Decay is normally confined to the roots and buttress zone (Rayner & Boddy, 1988; Watson & Green, 2011), though may also – albeit rarely – extend further up the stem (Mattheck et al., 2015). The host species may perhaps play a role in the location of the decay, with Quercus spp. usually having rot confined to the roots and butt, whereas in Platanus spp. decay may extend some metres up the stem (Schwarze & Ferner, 2003).

A slightly stalked and now-inactive Ganoderma resinaceum sporophore emanating from the butt of a mature Quercus robur.

Significance

Because Ganoderma resinaceum can spread into sound sapwood (Watson & Green, 2011) by breaching the reaction zone (Schwarze & Ferner, 2003), in addition to the ‘complete’ delignification induced by the mycelium within not only the butt but also the roots (Lonsdale, 1999; Schwarze & Ferner, 2003), there is a potentially high level of risk associated with retention of a specimen with a full crown, where the target area is significant. Ductile fracturing will typically be induced at the root plate or near to the base of the host (Mattheck et al., 2015), when the decay has advanced significantly (Watson & Green, 2011). Schwarze & Ferner (2003) do however note that the extent of decay may be less than where decay has been caused by other Ganoderma species (such as Ganoderma applanatum).

A fresh sporophore growing at the base of a fairly large Quercus robur.

Treatment and prevention

Limiting the severity of pruning operations is likely to reduce the risk of decay by this fungus, though care where working around the base of potential hosts is also important – given the fungus will colonise around the root plate and butt region (Mattheck et al., 2015). If found to be colonising a tree, if the target area includes people and / or property, strong consideration must be given as to at least pruning the tree (even if only a small reduction). Investigations into determining wood strength can be supplemented with the use of a resistograph, ultrasound tomography, or a fractometer (Deflorio et al., 2008a; Mattheck et al., 2015). However, as Ganoderma resinaceum may colonise sapwood very easily when the barrier zone is breached by invasive devices (Schwarze & Ferner, 2003), careful consideration as to what type of decay-detection device that is to be used is mandatory.

[…] If you’re wondering what on earth was going on with my last post, please rest assured that my little trek wasn’t all in jest. I found plenty of fungi and saw some awesome sights, and over the coming while I shall be sharing the best ‘scores’. Below is one of them, and oddly enough it’s a tree I have walked past so many times, but have never stopped to properly look. Thankfully, that changed today, and I spotted two glorious sporophores of the lacquered bracket Ganoderma resinaceum. […]